The present invention relates generally to optical communications and, more particularly, to high frequency optical millimeter wave generation and wavelength reuse.
To construct a simple base station and to generate a low-cost optical millimeter wave (mm-wave) there are two key technologies required to make radio-over-fiber (ROF) systems practical for commercial deployment. Schemes of wavelength reuse or centralized lightwave in a central office have been proposed and experimentally demonstrated. The common characteristic in the previous scheme is that the electrical local oscillator (LO) frequency for generating the optical mm-wave is half of the spacing between two first-order sidebands. For example, for a 40-GHz optical mm-wave generation, the LO frequency is 20 GHz, and the bandwidth for the external modulator (EM) also requires 20 GHz. To further reduce the requirement of LO frequency and bandwidth of the EM and reduce the overall cost, it has already been proposed by others to generate an optical mm-wave by a multiple double-frequency technique through properly adjusting DC bias on the EM. Optical mm-wave signals up to 50-GHz have been generated using this method. However, this technique cannot provide the function of wavelength reuse.
Accordingly, there is a need for a simplified technique to generate optical mm-wave signals and wavelength reuse.